The present invention is directed to a method for manufacturing an otoplastic and to an apparatus for the implementation of the method.
In standard manufacturing methods for producing otoplastics, an impression is first made of the auditory canal of the ear of a hearing-impaired person to be supplied therewith. A negative is then shaped from the impression. Only then can an otoplastic be manufactured that fits the shape of the auditory canal of the ear. Under certain conditions, the otoplastic must still be cut or ground after manufacture in order to eliminate casting errors. Since this procedure is expensive and time-consuming, manufacturers have attempted for some time to develop a method with which the manufacture of an impression and of a negative can be avoided.
Thus, for example, German published application 12 31 304 discloses a method in which a self-hardening plastic is coated on a base member simulating the basic shape of the auditory canal of the human ear and in which the coated base member is subsequently directly inserted into the auditory canal of the ear of the hearing-impaired person. The plastic adapts to the inside contour of the auditory canal and the coated base member remains in the auditory canal until the plastic hardens.
This method, however, involves several disadvantages. First, it is relatively dangerous for the hearing-impaired person to have a paste-like compound directly in his ear since a part of the compound can detach from the base member and be pressed too far into the auditory canal. Second, the hardening or curing process of the plastic produces heat that can be unpleasant for the unprotected ear. Further, this publication discloses an embodiment wherein the plastic chemically unites with the base member, this being again dangerous for the unprotected ear. Finally, a plurality of standard base members is required in this method, since the plastic coating is not adequate to sufficiently adapt to the many different shapes of auditory canals.
The article "A Tool for the Optimization of Hearing Aid Fittings" by Dr. Barry Voroba published in "Hearing Instruments", volume 35, No. 1, January 1984, pages 12 through 14 and 16, and United Kingdom application GB-A 2 084 072 likewise disclose methods in which a plastic is directly placed into the auditory canal of the ear. In these methods, soft plastic materials or compounds are injected into the ear. Suitable dies are then pressed into the compound before it hardens or cures. After hardening the compound and die are removed from the auditory canal of the ear. The dies are subsequently removed from the compounds and housing shells remain for in-the-ear hearing aids. These methods, however, likewise exhibit most of the disadvantageous of the afore-mentioned German published application 12 31 304. For example, the soft compound is also in direct contact with the auditory canal of the ear and the hardening process occurs in the unprotected auditory canal. Moreover, a plurality of standard base members are again required, this resulting in costs and materials.
German application AS 24 59 259 discloses a further possibility of manufacturing an ear adaptor member without the use of an impression or negative. Instead of an otoplastic, the sound channel of the hearing aid is held in the auditory canal with a surrounding pocket filled with liquid. The pocket adapts to the shape of the auditory canal due to a pressure ring which is pressed against the pocket. A disadvantage of this method is that the liquid in the pocket does not harden. Therefore, there is always the risk that the pocket will rip and the fluid will run out. A similar apparatus that has a fluid-filled pocket is disclosed in U.S. Pat. No. 3,602,654.
French patent A 1 552 471 discloses a bag filled with hardenable molding material that is used as an otoplastic after the hardening of the molding material. The subject matter disclosed therein differs from the present invention in that the in-the-ear hearing aid module is plugged into the hardened otoplastic and therefore projects from the ear after the hearing aid is positioned in the ear. A hearing aid constructed according to the present invention is embedded in the otoplastic and overcomes this disadvantage.
Furthermore, since the bag has a constant volume, it cannot be as well-adapted to a variety of shapes of auditory canals. Since, in contrast to the present manufacturing method, no axial pressure is exerted on the walls of the auditory canal in the adaptation, the bag does not reproduce the shape of the auditory canal as well as the present invention. In order to produce an adequate hold in the ear, the otoplastic of French patent A 1 552 471 is not only seated in the auditory canal but is also seated in the auricle of the outer ear. The subject matter of French patent 1 552 471 (equivalent to German published application 1 616 152) is summarized in the article "Verfahren zum Herstellen eines Ohrstueckes fuer ein Hoergeraet" in Neues aus der Technik, No. 2, 15 May 1986, page 2, Wuerzburg, Federal Republic of Germany.